Many of terminal apparatus such as mobile phone terminals which become popular lately include a variety of sensors such as acceleration sensors and luminance (environment light) sensors.
A sensor is a part of an electric circuit for converting a physical quantity including a magnitude of force, a length of distance and brightness into another type of physical quantity such as an electric signal. The mobile phone terminals use these sensors to improve the usability of the telephone units and to perform processes of a variety of applications.
A mobile phone terminal with an illuminance sensor is one example of applications of the above sensors. For example, it is conventional to change in a step-by-step manner the luminance value of light radiated from the light source of the backlight used for the display of the mobile phone terminal according to the output of the illuminance sensor. Generally, the illuminance sensor is provided adjacent to the display in order to detect the illuminance (brightness) around the display.